The patched (2) has smallest total time, since it has no cache hit overheadsand less I/O block time(thanks to async readahead). Here the I/O sizemakes no much difference, since there's only one single stream.

Note that (1-1)'s real I/O size is 64KB and (1-2)'s real I/O size is 128KB,since the half of the read-around pages will be readahead cache hits.